The present invention relates generally to a zoom lens, and more specifically to imaging apparatus incorporating a zoom lens, for instance, video cameras, and digital cameras.
In recent years, imaging apparatus such as digital cameras designed to take images of subjects using solid-state imaging devices such as CCDs or CMOSs have gone mainstream in place of silver-halide film cameras. Further, they have now a wide spectrum of categories from the commercial high-end type to the compact low-end type.
Users of such low-end type digital cameras would enjoy snapping shots over a wide range of scenes at any time in any place. For this reason, preference is given to small-format digital cameras, especially of the type that can be well put away in the pockets of clothing or baggage, are convenient to carry around, and are slimmed down in their thickness direction, and there is a mounting demand for size reductions, higher zoom ratios, and wider-angle arrangements of zoom lenses mounted on digital cameras or the like, too. On the other hand, as the pixels of imaging devices are now on the increase, there is also a mounting demand for the zoom lens to have higher optical performance.
To meet such demands, a zoom lens system of the type that has a lens group of positive refracting power located nearest to its object side has been proposed in the art. This type of zoom lens has the merit of easily achieving higher zoom ratios. Among prior zoom lenses having relatively high zoom ratios and compact format, for instance, there is a type comprising, in order from its object side, a first lens group of positive refracting power, a second lens group of negative refracting power, a third lens group of positive refracting power and a fourth lens group of positive refracting power, as set forth in the following patent publications.
[Patent Publication 1]
JP(A) 2006-330657
[Patent Publication 2]
JP(A) 11-52244
[Patent Publication 3]
JP(A) 2007-3554
For the lenses proposed in Patent Publications 1, 2 and 3, however, much is still desired in terms of size reductions, because the first lens group is thick as a whole and the full length of the lens system is large relative to an image height.
Having been made in view of such problems as mentioned above, the present invention has for its object the provision of a zoom lens system of the type having a lens group of positive refracting power located nearest to its object side, which works for making sure size reductions and optical performance. Another object of the invention is to provide an imaging apparatus using such a zoom lens.